/*
 * DateTransform.java May 2007
 *
 * Copyright (C) 2007, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.transform;

import java.util.Date;

/**
 * The <code>DateTransform</code> object is used to transform date
 * values to and from string representations, which will be inserted
 * in the generated XML document as the value place holder. The
 * value must be readable and writable in the same format. Fields
 * and methods annotated with the XML attribute annotation will use
 * this to persist and retrieve the value to and from the XML source.
 * <pre>
 *
 *    &#64;Attribute
 *    private Date date;
 *
 * </pre>
 * As well as the XML attribute values using transforms, fields and
 * methods annotated with the XML element annotation will use this.
 * Aside from the obvious difference, the element annotation has an
 * advantage over the attribute annotation in that it can maintain
 * any references using the <code>CycleStrategy</code> object.
 *
 * @author Niall Gallagher
 */
class DateTransform<T extends Date> implements Transform<T> {

    /**
     * This represents the constructor used for creating the date.
     */
    private final DateFactory<T> factory;

    /**
     * Constructor for the <code>DateTransform</code> object. This is
     * used to create a transform using a specified date format. The
     * format should typically contain enough information to create
     * the date using a different locale or time zone between read and
     * write operations.
     *
     * @param type this is the type of date to be created by this
     */
    public DateTransform(Class<T> type) throws Exception {
        this.factory = new DateFactory<T>(type);
    }

    /**
     * This method is used to convert the string value given to an
     * appropriate representation. This is used when an object is
     * being deserialized from the XML document and the value for
     * the string representation is required.
     *
     * @param text the string representation of the date value
     * @return this returns an appropriate instanced to be used
     */
    public synchronized T read(String text) throws Exception {
        Date date = DateType.getDate(text);
        Long time = date.getTime();

        return factory.getInstance(time);
    }

    /**
     * This method is used to convert the provided value into an XML
     * usable format. This is used in the serialization process when
     * there is a need to convert a field value in to a string so
     * that that value can be written as a valid XML entity.
     *
     * @param date this is the value to be converted to a string
     * @return this is the string representation of the given date
     */
    public synchronized String write(T date) throws Exception {
        return DateType.getText(date);
    }
}
